1. Field of the Invention
This invention relates to an imaging or image forming material which enables image formation and storage by the electrophotographic process based on the electrostatic latent image to be performed by a simple operation comparable to that for instant photography.
2. Prior Art
In the field of image forming technique, a system in which a uniformly charged photosensitive member is selectively irradiated with light in accordance with image signals, and wherein the electrostatic image thus formed is developed, is generally termed an electrophotographic process. This electrophotographic process is roughly classified into a dry developing method and a wet developing method.
The wet developing method means a system in which an electrostatic latent image formed on a photosensitive member is developed using a liquid developer produced by dispersing the dye or the pigment as the colorant in the form of fine powders in an insulating medium. Research and development is currently conducted in various phases of the wet developing method since the resolution and the gradation comparable with that of the halide photograph may be achieved, and wherein the image exhibits superior weatherability, particularly when the pigment is used as the colorant.
The majority of the liquid developers for wet development now being evolved are a liquid developer making use of a substance which is liquid at room temperature and which is represented by a saturated hydrocarbon insulating medium such as Isopar G manufactured by ESSO. However, this liquid developer has a drawback such that it is inferior in handling properties and operability, while being insufficient in image reproducibility due to susceptibility of the colorant particles to flocculation and precipitation, and that a separate step of waste liquid disposal is necessitated.
For overcoming the above problem, the present Applicant has proposed in the Japanese Patent Application 63-156846 (1988) an electrostatic latent image developer which is produced by dispersing colorant particles in an electrically insulating organic material which is solid at ambient temperature.
Meanwhile, the above mentioned electrostatic latent image developer is markedly superior to the liquid developer in operability or handling/storage properties, and is usually contained in a developer tank in the state of being ready for usage. However, there is still ample room for simplifying or reducing the size of the device for development or shortening the developing time with respect to application of the developer.
For practical usage, it is desirable that the developed electrostatic latent image be recorded and stored in a directly visible form. Although the latent image is conventionally transferred to a suitable transfer medium, such as paper, the transfer efficiency is lowered due to too strong adsorption between the colorant particles and the photosensitive member, which lowers the image quality.